SHPE Foundation SHPE Jr. Chapter Curriculum Hands-on Activity Training TeachEngineering Hands-on Activity: * Light Intensity Lab TeachEngineering Digital Library: teachengineering.org

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General Advice Be prepared! Do each activity beforehand Make sure all materials are available Keep students on task Follow the time frame Be flexible Have Fun!! SHPE Foundation SHPE Jr. Chapter Curriculum Hands-On Activity Training

Light Intensity Lab Light intensity, light attenuation Engineering focus: o Engineering Research/Analysis Perform an experiment to observe the relationship between light intensity and attenuation layers. Develop a rule (equation) based on empirical data that can be used in future applications. Learning objectives: o Derive the relationship between light intensity and the number of layers of attenuation. o Perform experiments to illustrate the concept of attenuation. SHPE Foundation SHPE Jr. Chapter Curriculum Hands-On Activity Training Full Activity on TeachEngineering

Light Intensity Lab Suggested time: 50 minutes Suggested group size: 3 students/group Materials (per group): lamp Incandescent 60W bulb (not halogen) 12 x 12 piece of aluminum foil clean transparencies printed light intensity scale (print each one, photocopies may not show the correct grayscale detail)light intensity scale 12 masking tape scissors Access to Excel or a graphing calculator Light Experiment Handout (student version) For the instructor: Light Experiment Handout (teacher version) SHPE Foundation SHPE Jr. Chapter Curriculum Hands-On Activity Training

Light Intensity Lab SHPE Foundation SHPE Jr. Chapter Curriculum Hands-On Activity Training Engineering Connection (Real World Application): Light attenuation and Beer's Law are engineering concepts that are very important for many engineers. Environmental engineers use this concept when building solar panels as a means of alternative energy. NASA has used the concept of attenuation (with radio waves) to determine information about Saturns rings. Biomedical engineers use these concepts in the design of x- ray machines, and also in other broader applications such as the field of biomaterials. o In this activity, measuring bone mineral density using x- ray machines is used as the motivation engineering connection for the experiment.

Light Intensity Lab SHPE Foundation SHPE Jr. Chapter Curriculum Hands-On Activity Training Vocabulary TermsDefinitions/Equations Beers Law Light Attenuation The loss of light intensity as light passes through a material. The extent of attenuation is based on the light entering the material and properties of the material. Light Intensity

Light Intensity Lab SHPE Foundation SHPE Jr. Chapter Curriculum Hands-On Activity Training Activity Procedure: Before the Activity: o Make sure each group is able to work at a table pushed up against a wall to shine the lamp onto and take intensity measurements (limit the group numbers/ increase the group size if necessary). o Experiments must be performed with the room lights turned off and the shades drawn – only using light from the lamps. o Make copies of the worksheet for each group. o Set out materials at each work station.

Light Intensity Lab SHPE Foundation SHPE Jr. Chapter Curriculum Hands-On Activity Training Activity Procedure: With the Students: o Tape the light intensity scale to the wall just above the surface of the table, and set up the lamp to shine on the scale (do not turn on the lamp yet). o Cut the transparency into eight equal-sized pieces. o Take a piece of foil and cut a 5 mm diameter hole in the center of it. o Next, cover the face of the lamp by wrapping the aluminum foil around it, making sure that the hole is in the center of the face of the lamp and that the foil does not cover the vents in the back of the lamp.

Light Intensity Lab SHPE Foundation SHPE Jr. Chapter Curriculum Hands-On Activity Training Activity Procedure (cont.): o Darken the room, turn on the lamp, and hold a piece of transparency a couple inches from the wall to cast a shadow near the scale (but not on the scale). o Match the intensity of the resulting shadow on the wall with a square on the scale. (Note: Its easier to distinguish the matching shade of gray if you step back to look at it.) o Record the intensity in Table 1 on the first page of the worksheet. o Repeat the process with two sheets of transparency stacked together, then three, and so on until the table is filled. o Use Excel to plot the natural logarithm of the shadows intensity versus the thickness of the attenuator. (Instructions provided on the worksheet – if computers are not available, have students use graphing calculators and graphing paper to create this graph.)

Light Intensity Lab SHPE Foundation SHPE Jr. Chapter Curriculum Hands-On Activity Training Thickness = Number of Transparencies Light IntensityNatural Log of Intensity = ln(intensity) Sample Results

Light Intensity Lab SHPE Foundation SHPE Jr. Chapter Curriculum Hands-On Activity Training Teaching tips: o Emphasize the science concepts, vocabulary, and engineering connection; reinforce these throughout the activity. o Ask students if they have ever had an X-ray. Explain that the concepts explored in this activity are what allowed engineers to develop X-ray technology! Ask them if they think they would have healed from injuries as well if doctors were not able to use X-rays. o Once students have made their graphs, discuss the results as a class. Ask students if they discovered a relationship between the layers of attenuation (layers of transparencies) and the light intensity. Ask them what this suggests about light (or x-rays) passing through dense materials versus less dense materials. o Have fun and encourage students to have fun!!

Activity Takeaways Teambuilding skills o Making decisions, sharing tasks and materials Engineering skills o Engineering Analysis : performing an experiment, taking quantitative measurements, analyzing results, relating results to real world problems and technologies. SHPE Foundation SHPE Jr. Chapter Curriculum Hands-On Activity Training Encouragement through life experiences o Relate this activity to the experience of having an x-ray. Emphasize how students are discovering the concepts involved in designing an X-ray machine. Motivation through having fun o Introduce the activity as a fun learning experience!

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